1. Field of the Invention
This invention relates to a medium for testing a microorganism for biochemical behavior. More particularly, this invention relates to an improved medium to be used in performing lysine decarboxylation test on microorganisms such as enteric bacteria by the method of biochemical identification.
For administration of a proper medication to a patient of an infectious disease, it is essential to identify a pathogenic microorganism responsible for the disease, subjecting the patient to a sensitivity test, and selecting an effective medicine. In the identification of such a pathogenic microorganism, many biochemical tests are performed. One of them is an lysine decarboxylation test. The medium of this invention is advantageously used for the lysine decarboxylation test.
2. Description of the Prior Art
The lysine decarboxylation test is intended to detect a microorganism which decarboxylates L-lysine into cadaverine and carbon dioxide. At present, it is one of the most important tests performed on microorganisms for biochemical behavior. This test is carried out by culturing a given microorganism on a medium containing L-lysine and a pH indicator as main components. As the medium to be used in this test, a composition formed of trypton T, glucose, monosodium dihydrogen phosphate, L-lysine monohydrochloride, bromothymol blue, and purified water has been recently proposed [Japanese Patent Publication No. SHO 58(1983)-20,263]. This medium permits the time required for culture to be notably decreased as compared with the conventional countertype. Specifically, the culture time has been one to two days in the conventional medium, whereas it is four to five hours in the medium under discussion, making it possible to conduct the test and find the result of the test on one same day. Depending on the kind of the microorganism under test, however, the culture performed for four to five hours in this medium does not permit the reaction to proceed sufficiently for required evaluation. In this case, the culture time must be elongated and the evaluation of the test result made on the following day. In the circumstance, the desirability of developing a medium in which any microorganism can be cultured sufficiently in a matter of four to five hours to permit clear distinction between positive and negative test of the reaction has found growing approval.
For early medication, the identification of a pathogenic microorganism is desired to be carried out as rapidly as permissible. There are, however, times when the evaluation of the test result is compelled to be performed on the following day because of the convenience of the work involved in the test. In this case, the medium is desired to be such that the culture time is not rigidly specified and, therefore, the culture time may be elongated to suit the convenience of the work and, despite the elongation of the culture time, the reaction is not suffered to proceed excessively and the evaluation of the test result can be conducted accurately.
For the efficiency of work involved, many biochemical tests are frequently performed all at once by the use of a multi-well culture plate. Thus, it becomes necessary for culture times of different test items to be equalized to one another. Again in this case, the culture medium is desired not to involve any rigid limitation of culture time.
An object of this invention, therefore, is to provide a novel medium for lysine decarboxylation test.
Another object of this invention is to provide a medium which does not specifically limit culture time and enables the identification of the pathogenic microorganism to be performed on the same day as the culture is carried out or on the day following the culture.
A further object of this invention is to provide a medium for lysine decarboxylation test which permits a color reaction to produce a distinct color and enables the evaluation of test result to be effected with ease.